Electronic devices, such as a computer and a network device, are interconnected with a plurality of devices in order to increase the data processing capability and a data processing capacity. Since the floor space is limited, a plurality of electronic devices is collectively loaded in a rack. The processing speed and the processing capability of those electronic devices have been improving rapidly, and the amount of heat generated in such an electronic device is increasing steadily. Conversely, those electronic devices have a temperature environment set to be relatively low for a normal operation. Hence, heats generated in the electronic devices loaded in the rack are cooled by cooling the electronic devices and evacuated to the exterior of the electronic devices as exhaust air after the cooling. However, when heats by such exhaust air remain in the rack and the temperature inside the rack increases, the electronic devices may become unable to operate appropriately.
Accordingly, exhaust air from the electronic devices is evacuated to the exterior of the rack in order to suppress a temperature rise inside the rack. However, air utilized for cooling the electronic devices is air (room air) in the room where the rack is placed. Hence, when the temperature inside the room rises due to the exhaust air from the rack, the cooling performance for the electronic devices by the room air decreases. Moreover, when a plurality of racks is placed in the room, exhausted heats from respective racks may interfere with each other, and an area so-called a hot spot is produced where a temperature is locally high. When the rack is located in such a place, the cooling performance for the electronic devices by the room air further decreases.
In order to address this technical issue, Patent Literatures 1 to 5 disclose technologies relating to a cooling apparatus for cooling exhaust air from electronic devices by utilizing the vaporization-condensation cycle of a coolant. According to this cooling apparatus, exhaust air from an electronic device is directed to a heat exchanger, and is cooled by the latent heat by the vaporization of the coolant circulating in the heat exchanger.
Such a cooling apparatus operates as follows.
Air heated in the electronic device is evacuated as hot exhaust air from the rear face of the electronic device by a fan built therein, and passes through an evaporator (hereinafter, referred to as an evaporator unit) serving as the heat exchanger placed on a rear door of the rack or an inner door, etc., inwardly of the rear door. At this time, a fluid coolant (coolant fluid) charged in the evaporator unit and having a low boiling point removes heat from the exhaust gas from the electronic device, the exhaust gas passing through the evaporator unit, vaporizes, and changes the phase from a fluid (the coolant fluid) to a vapor (a coolant vapor). The exhaust air from the electronic device is mainly cooled by the latent heat derived from such phase change, and is evacuated to the exterior of the rack. When the coolant changes the phase thereof from the fluid to the vapor, the volume thereof increases, and thus the pressure of the coolant vapor increases. The coolant vapor having the pressure increased moves, due to pressure gradient, to a condenser unit where a pressure is low. The coolant vapor is cooled by the condenser unit to dissipate heats, changes the phase thereof to the coolant fluid, and flows back to the evaporator unit again. The exhaust air, in a cooled condition, from the electronic device is returned in this manner from the rack to the interior of the room. Accordingly, a temperature rise of the interior of the room where the rack is placed can be prevented, and the cooling performance for the electronic devices by the room air can be maintained well.